Having a Guardian Angel in your inventory will completely negate the XP loss.

A Revive from a Cleric will reduce the XP loss by (ResLvl-1)*10%. So if a Cleric with Lvl 9 Revive casts on a dead player with Culti Lvl 69, the player will lose 2%*[1-(9-1)*10%] XP, or 0.4% of his current level.